1. Field of the Invention
This invention relates to equipment useful in high frequency radio communications systems. More particularly, the invention is concerned with a polarization rotator for changing the polarization of signals passing through a waveguide.
2. Description of Related Art
Rotator elements placed in-line with a waveguide are useful for changing the polarization of a signal prior to further processing. Waveguides associated with antennas may include polarization rotation functionality, for example, to allow conversion of the antenna between horizontal and vertical polarization, without requiring rotation of the entire antenna assembly.
The geometries of in-line polarization rotation elements are well known in the art. Transition elements inserted into the electrical signal path progressively rotate the signal through a desired angular rotation, such as ninety degrees between “vertical” and “horizontal” polarization or vice versa. The transition elements may be provided as a plurality of plates, layers or the like. However, these additional elements increase the total number of parts, complicating manufacture. Further, the plurality of layers may introduce alignment and/or signal leakage issues between each of the several plates/layers.
Alternatively, the transition elements may be applied as a plurality of pins extending across the waveguide. However, insertion and sealing of each pin end at the waveguide sidewalls may be labor-intensive. U.S. Pat. No. 2,628,278 “Apparatus for Rotating Microwave Energy” issued 20 Sep. 1951 to J. F. Zaleski discloses an adjustable circular waveguide polarization rotator that utilizes a twisted septum element suspended within a waveguide by pins at each end coupled to sidewalls of two rotatable body portions of the waveguide. By twisting the body portions with respect to each other, the septum is twisted to obtain a desired polarization angle transition. Although the required number of sidewall pin interconnections is reduced, the thin septum element suspended between the pins may be susceptible to vibration, sagging and/or other forms of distortion over time.
Depending upon the equipment combination used, a waveguide cross-section transition between, for example, a circular to rectangular waveguide may also be required as a further additional component located, for example, between an antenna and a transmitter or receiver.
Competition within the waveguide and RF equipment industries has focused attention upon improving electrical performance, reduction of the number of overall unique components, as well as reductions of manufacturing, installation and or configuration costs.
Therefore, it is an object of the invention to provide an apparatus that overcomes deficiencies in the prior art.